This invention relates to grinding wheels and specifically the abrasive mixture which is formed and then molded or pressed into the final grinding wheel.
There is a class of grinding wheels which are used in so-called precision grinding which is a grinding process involving the use of a grinding coolant and is therefore termed wet grinding. Precision grinding is important in various operations, such as in the cutlery trade to form edges on knives and scissors as well as in grinding of steel rolls or in centerless grinding and between centers grinding to form parts accurately to size and required finish.
In precision grinding it is the practice to use a grinding coolant in what may be termed as wet grinding. The conventional grinding coolant is usually water based and includes rust inhibitors and grinding aids.
Precision grinding traditionally has been performed by conventional pressed vitrified or resin bonded wheels.
A new class of wheels now being used in these operations are bonded using liquid resins such as epoxies, polyester or other engineering resins. These wheels are cast to size rather than formed in hydraulic presses.
In order to improve the grinding action of this type of wheel it has been determined that it is beneficial to induce a controlled amount of porosity in the wheel.
Several materials such as Alumina bubbles, silica spheres, and micro balloons have been used for this purpose. All of them have exhibited shortcomings or excessive cost that have reduced their effectiveness as pore formers.
It is accordingly an object of the invention to provide a grinding wheel containing a dissolvable granular material which is sufficiently coarse to provide a controlled induced porosity to aid the free grinding action of the grinding wheel.
Another object of the present invention is to provide a grinding wheel containing water soluble granular material which will stay essentially unchanged during the manufacturing process.
Yet another object of the present invention is to provide a grinding wheel containing dissolvable granular material which does not add undue expense and which does not adversely effect the strength of the wheel.